1. Field of the Invention
This invention relates to medical diagnosis and, in particular, to a technique for determining a patient's level of cell-mediated immunity.
2. Description of the Prior Art
As understood in the art, cell-mediated immunity is a form of nonspecific and/or acquired immunity involving various white blood cells, particularly, lymphocytes of thymic origin, i.e., T-lymphocytes, and monocytes. Immunity of this type is responsible for resistance to infectious diseases caused by certain bacteria, fungi and viruses, and plays a role in certain allergies. Cell-mediated immunity is also involved in certain aspects of an individual's resistance to cancer, in delayed hypersensitivity reactions, certain autoimmune diseases and in the rejection of allografts.
Lymphocytes and monocytes are the main effector cells involved in cell-mediated immunity. In response to various stimulants, these cells influence each other both by physical contacts and by the release of active substances, i.e., lymphokines and monokines. Changes in the mutual interactions of these cells generally result in changes in the level of cell-mediated immunity exhibited by the body in response to challenges.
The level of cell-mediated immunity expressed by patients varies with the character and stage of their disease. It is increased in allergic and autoimmune diseases, especially during their acute stages.
It is suppressed in cancer and some other diseases, as for instance in some systemic diseases (lupus erythematosus, multiple sclerosis), in the acute stage or in exacerbation of bacterial diseases such as tuberculosis and leprosy, in acute viral diseases, in bacterial intoxications, as well as in the course of immunosuppressive therapy using corticosteroids, antithymocyte immune globulin (ATG) or cyclosporin A. Also, some noninfective diseases, e.g., diabetes, as well as traumas and surgical operations, may be complicated by the suppression of cell-mediated immunity.
The suppression is often associated with an unfavorable outcome for the patient. Successful treatment of the patient's disease manifests itself by the normalization of the cell-mediated immune response of the body. Consequently, evaluation of cell-mediated immunity provides important information concerning the state of the patient and the efficacy of the treatment applied.
In addition to providing a method for evaluating the course of treatment of such diseases as cancer, the ability to determine an individual's level of cell-mediated immunity has numerous other important clinical and experimental applications. For example a method for evaluating the level of cell-mediated immunity can be used to study acquired and genetically determined immunodeficient states. It can also be used as a screening method to determine serum factors which suppress or alter the cell-mediated immunity response. Further, a method for determining the level of cell-mediated immunity can be used to study the mechanisms of lymphokine and monokine production and regulation. A discussion of these and other applications for methods for measuring cell-mediated immunity can be found in the recent review entitled Immunodiagnosis of Cancer, edited by Ronald B. Herberman and K. Robert McIntire, Marcel Dekker, Inc., New York, 1979. See in particular chapter 5.3, entitled "Application of the Microculture Lymphocyte Proliferation Assay to Clinical Studies," Jack H. Dean, Litton Bionetics, Inc., Kensington, Md., pages 738-769.
At present, a patient's level of cell-mediated immunity is determined through a battery of tests, usually applied concurrently. The level of cell-mediated immunity is determined by comparing and summarizing the results of the various tests. One such test which has been used to evaluate the level of cell-mediated immunity has involved the reaction of leukocytes to mitogens.
Mitogens are agents which stimulate cell division, i.e., mitosis. Among the mitogens used for immunological assays are mitogenic lectins extracted from plants, such as, Concanavalin A (Con A) and phytochemagglutinin. These agents are effective in inducing proliferation of T-lymphocytes.
Mitogens are used to determine a patient's level of cell-mediated immunity by measuring the extent of lymphocyte activation and proliferation induced in response to a mitogen. The intensity of DNA or protein synthesis by lymphocytes is used as a marker of lymphocyte activation in such assays. A radio-labeled precursor of DNA, e.g., thymidine, or of protein, e.g., leucine, is added to a suspension of mitogen-stimulated lymphocytes taken from the patient whose level of cell-mediated immunity is to be determined. Incorporation of the labeled material into the patient's lymphocytes is measured and compared with the level of incorporation by normal lymphocytes.
Use of this method gives information regarding the level of cell-mediated immunity based on the response of lymphocyte cells. Significantly , it does not provide information regarding the monocyte component of the cell-mediated immunity response.
The activity of monocytes and monocyte-derived macrophages is measured by their capacity to ingest particles (phagocytosis) and by their migration toward certain antigens (macrophage migration or chemotaxis). None of these tests for monocyte and monocyte-derived macrophages have used mitogens and, in particular, none of these tests have used mitogens for the evaluation of macrophage and monocyte behavior in the cell-mediated immunity response.
Monocytes and monocyte-derived macrophages are known to display the ability to fuse and to form polynuclear cells (hereinafter referred to as polykaryons) under various pathological and experimental conditions. Specifically, the polykaryons generally appear in inflammatory foci elicited by the same immunological stimuli, e.g., bacteria, fungi and viruses, which cause the establishment of cell-mediated immunity, as well as in cell cultures. Such an ability has never been used for evaluation of cell-mediated immunity.
In summary, to date, mitogens have been used to evaluate levels of cell-mediated immunity only by their influence on proliferation of lymphocytes. The proliferation has been assayed by means of the incorporation of radio-labeled precursors of DNA or protein into the lymphocytes undergoing proliferation.